I just got a Skil 20V brushless leaf blower that I like, but the blower tube is a bit short and pretty basic. I looked for an accessory tip/concentrator but did not see any. This is a quick-and-dirty remix in OpenSCAD to add a twist-lock fitting and slightly scale the original .STL (by 3DPossible) to fit the 84mm OD of the Skil blower tube. It fits tightly on purpose.

Print using supports, and I used concentric top, bottom and fill.

You can drop part of the coupling down below your build plate to shorten the coupling as desired. (I did!)